Hi there Hoc,
I was looking at your accepted equipment and I think there are some things you would like to add in order to make in More Celtic.
2 things you are missing right off the bat are the 1h " Scottish Sword" and the Longbow. The Longbow is a Welsh creation. (Welsh being a Celtic/Gaelic peoples).
Also Celtic style shields were more Oval and elongated (since the shield was often the only source of protection)and less round like the Norse ones you have selected. Celtic helmets were more like what the Romans used, with a lip over the brow. In-fact the Romans basically used the Celtic design for helmets and may have also gotten the idea for their shields from the Celts. Finally, it is widely believed that chain-mail and the longsword were first designed by Celts, so anything in relation to that should be approved (within reason of esthetic design).
Also, for throwing weapons, you should put more emphasis on throwing javelins (very Irish) rather than throwing axes (which again is more of a Norse/ Frankish thing).
Oh and, your most fanatical members should just fight naked with a big ass shield and sword (very Gaul like).
All the best,
Helm